Fracture mechanics

Modeling micromechanics and crack propagation in laminated fiber reinforced composites

Crack propagation is among the predominant modes of failure in many engineering structures, often leading to severe loss of structural integrity. In laminated fiber reinforced composites, which are among the most promising structural materials for the aerospace and automotive industries, modeling crack propagation is more challenging than conventional brittle/ductile materials due to the presence of large process zones behind the crack tip. These process zones, also known as bridging zones or cohesive zones, are regions of complex fiber-matrix micromechanics which significantly enhance the fracture toughness of these materials. To address this modeling problem, we have developed a framework for cohesive crack propagation based on the variational multiscale method. It treats cracks as displacement discontinuities and represents them as fine scale variations with compact support on a coarse scale displacement field. This treatment leads to a multiscale model with a coarse scale problem enforcing the conservation of linear momentum and a fine scale problem representing the micromechanics (cohesive surface laws). The formulation was demonstrated through various benchmark problems and validated by extensive comparison with experiments.


S. Rudraraju, A. Salvi, K. Garikipati, A. M. Waas, ``In-Plane fracture of laminated fiber reinforced composites with varying fracture resistance: experimental observations and numerical crack propagation simulations'', International Journal of Solids and Structures (IJSS), Vol 47, Issues 7-8, Pages 901-911, 2010. [journal] [arXiv]

S. Rudraraju, A. Salvi, K. Garikipati, A. M. Waas, ``Predictions of crack propagation using a variational multiscale approach and its application to fracture in laminated fiber reinforced composites'', Composite Structures, Vol 94, Issue 11, Pages 3336-3346, 2012. [journal]

S. Rudraraju, A. Salvi, K. Garikipati, A. M. Waas, ``Experimental observations and numerical simulations of curved crack propagation in laminated fiber composites'' Composites Science and Technology (CST), Vol 72, Issue 10, Pages 1064-1074, 2012. [journal]

S. Rudraraju, K. Garikipati, A.M. Waas, B.A. Bednarcyk, ``On the Theory and Numerical Simulation of Cohesive Crack Propagation with Application to Fiber-Reinforced Composites'', NASA Technical Publication(peer reviewed) (NASA/TP-2013-217431, E-18123), 2013. [NASA]

Shown here are the displacement discontinuity capturing shape function, crack propagation in the SETB and CT geometries and the micro-mechanical model of the fiber pull-out.

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